Create 2014. Longest Subsequence Repeated k Times

2014. Longest Subsequence Repeated k Times

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+class Solution {
+public:
+    bool isKRepeatedSubsequence(const string& s, const string& pattern, int k) {
+        int pos = 0, matched = 0;
+        int m = pattern.size();
+
+        for (char ch : s) {
+            if (ch == pattern[pos]) {
+                pos++;
+                if (pos == m) {
+                    pos = 0;
+                    matched++;
+                    if (matched == k) return true;
+                }
+            }
+        }
+        return false;
+    }
+
+    string longestSubsequenceRepeatedK(string s, int k) {
+        vector<int> freq(26, 0);
+        for (char ch : s) freq[ch - 'a']++;
+
+        vector<char> candidates;
+        for (int i = 25; i >= 0; --i) {
+            if (freq[i] >= k) candidates.push_back('a' + i);
+        }
+
+        queue<string> q;
+        string ans = "";
+
+        for (char ch : candidates) {
+            q.push(string(1, ch));
+        }
+
+        while (!q.empty()) {
+            string curr = q.front(); q.pop();
+
+            if (curr.size() > ans.size() || (curr.size() == ans.size() && curr > ans)) {
+                if (isKRepeatedSubsequence(s, curr, k)) ans = curr;
+            }
+
+            if (curr.size() == 7) continue;
+
+            for (char ch : candidates) {
+                string next = curr + ch;
+                if (isKRepeatedSubsequence(s, next, k)) q.push(next);
+            }
+        }
+
+        return ans;
+    }
+};